Ivabradine with 'normal' HR?

Even before I was diagnosed with POTS, I was prescribed beta blockers to help with my resting heart rate of over 120. And it helped! I'm usually at around 80 now when sitting, 72 when I'm about to sleep.

I got diagnosed with POTS two months ago and my cardiologist prescribed me ivabradine in addition to the beta blockers. 5mg in the morning and evening. However, I read that it shouldn't be taken if your HR is below 70. It's rare but my HR is currently at 60 and it was around 60 yesterday as well. Though I'm simply lying in bed and doing nothing. It's never this low when I'm being active, which I rarely am due to me/cfs. I would say I'm at around 70-80 most of the time when I'm chilling in bed but still. I'm obviously not checking my pulse 24/7.

Is it safe to take ivabradine? I'm honestly so scared but my cardiologist really thinks I could benefit from it.